The present invention relates generally to distributed communication systems, in particular, telephony-over-local area network (LAN) (ToL) communication systems and the like, and more specifically to a system and method for providing emergency call diversion in a distributed communication system.
Distributed communication systems such as telephony-over-LAN (ToL) communication systems, and the like are highly complex networked systems containing a plurality of elements or devices for routing calls to users of the system. For example, an exemplary ToL system might include a network having two or more sub-networks, each sub-network including a plurality of clients providing communication services to multiple users. Such a ToL system may further include one or more gatekeepers for assisting in the routing of calls to destinations within the system, a gateway for interconnecting the ToL system with an external switched circuit network such as the public switched telephone network (PSTN) or a private branch exchange (PBX), a multipoint control unit (MCU) providing support for conferences of three or more clients, a messaging server, a feature server, and the like. Thus, for example, an external call might enter the system through a gateway, and with the assistance of a gatekeeper eventually reach a client terminal such as an IP (Internet Protocol) telephone or the like. If after a predetermined number of rings the call remains unanswered, the call may be passed to a message server so that a voice mail message may be recorded for the user. When an event such as a power failure, a network or sub-network outage, or a site closure due to weather or disaster renders elements of a ToL system inoperative, it is desirable to divert calls received during the event to a messaging server, voice-mail server, or the like so that the call may be answered. In conventional communication systems, which have a single point of entry for all calls, emergency call diversion may be accomplished by placing the call diversion function in a single device at the point of entry for the calls. Thus, a common diversion behavior is provided for the entire system. For example, in PBX systems, a night mode or bypass mode may be provided for diverting calls to another number, a message server, or to a special emergency telephone. However, in ToL systems calls may enter the system at multiple points and may be processed by multiple devices within the system. Thus, it may be impossible to accomplish call diversion in all cases by accessing a single device since, depending on the elements affected by the particular outage, call diversion must be implemented at different points within the system. Accordingly, a system administrator would need to reset parameters in many places within the system to accomplish call diversion in all cases. Moreover, different events may cause outages of different elements within the system, making different call diversion behaviors desirable or necessary depending on the type of call received.
Consequently, it is desirable to provide a distributed communication system capable of providing emergency call diversion during an event such as a power outage or the like. Such a communication system would employ a mechanism allowing elements within the system affected by an outage to rapidly inform one another that it is necessary to enter a call diversion state so that calls may be diverted from different points within the network as necessary.